Conventionally, as a method of increasing the amount of data transmitted without increasing the number of signal lines, there is a technique in which other data signals are superimposed on a pair of two differential signal lines. As such a technique, there is, for example, a signal transmission apparatus in which two common-mode filters are provided to respective two signal lines of a pair included in a differential transmission path, by which single-ended mode signals of two channels are superimposed on each other using two signal lines that transmit a pair of differential signal lines (see, for example, Patent Literature 1).